Different age chicks, emergency please help!

Ok so I have 18 chicks total. Seven are six weeks old as of yesterday, six of them will be four weeks old Friday and I just got five more today that are about two days old. Of the seven, six are silkies and one is a Rhode Island Red, who is a rooster. The 3 1/2 week olds are all black australorps. The new ones are all Rhode Island Red sexed hens. My problem is that my Rhode Island Red rooster seems is being very aggressive with the new chicks. For instance the new chicks went eat in front of him and he picked them up from their heads and dropped them. He did this to about three. I've now seen him run at them and at one point pull their little fluff out. To add onto the new chicks pain the silkies don't seem to be that nice however, when we got the black australorps some of they acted as if they were their own chicks and seemed to protect them. Will that happen with these new chicks? Also one of the ba chicks who I know is a rooster pecked the head of one of the new chicks. Will they kill the news chicks? Sorry for all of the writing but I figured you guys needed to know the background and how old they all are. Please help!

Well it seems to me that they are just all sorts of stressed out is all. You have a lot of newbies that are trying to establish their own pecking order and then a new bunch gets introduced and they have to start all over again and to top it off you have a roo in there who will always place himself at the top of the order and fight anyone who challenges that . The roo that is typical behavior the hens yes sometimes if the order has not been made yet as to pecking.
As long as they don't draw blood and keep drawing blood it looks a lot worse than it really is. They peck me sometimes when I'm taking eggs from under them and it doesn't break the skin that's all they are doing to them. And of course children (chicks) make everything out to be worse than it really is so they are likely screaming bloody murder!!
As long as no blood I allow it to happen so they can establish their order sooner.

Ok so I left them in my brooder, which is a giant dog cage with wiring at the bottom. It's supposed to stop little chicks from escaping and wandering. When I put them in there all of newbies were all huddled together in the front of the door. When I came back my five little rir chicks were outside the brooder and shaking. When I put them back in there I put yogurt in there for the older chicks to distract them a little bit. All of them were eating with a few on the back end waiting their turn. My rir roo just walked over to them as they were eating and pecked a few of them. Soon after one the little ba Roos ran over and grabbed a little chick and shook it by its head violently. It then repeated the same thing to another chick that was right next to it. Even a couple of the silkies came over and pecked the new chicks but only on the body. How should I take this? I am prepared to set up another brooder for them tomorrow if need be. Please help!

Ok so I left them in my brooder, which is a giant dog cage with wiring at the bottom. It's supposed to stop little chicks from escaping and wandering. When I put them in there all of newbies were all huddled together in the front of the door. When I came back my five little rir chicks were outside the brooder and shaking. When I put them back in there I put yogurt in there for the older chicks to distract them a little bit. All of them were eating with a few on the back end waiting their turn. My rir roo just walked over to them as they were eating and pecked a few of them. Soon after one the little ba Roos ran over and grabbed a little chick and shook it by its head violently. It then repeated the same thing to another chick that was right next to it. Even a couple of the silkies came over and pecked the new chicks but only on the body. How should I take this? I am prepared to set up another brooder for them tomorrow if need be. Please help!

Its pretty much "tomorrow" now, hopefully the chicks are alright. I would recommend some separations, even if its only the roo in a small temporary cage away from smallest. It will greatly help if you give the smallest chicks places to hide, or like an area the bigger birds can't go with their own food/water(think wire dog crate or fencing/hardware cloth the babies can fit through and the larger ones can't?

I am relieved to tell you guys that all of my chicks have survived the relentless onslaught of pecking and bullying. I have a new brooder set up just for them and they love it. I took them outside in their run with my supervision and what do you know it. Ronald, my dominant roo came running over very aggressively with his posse of ba Roos. All of my ba Roos will be sold because they have terrible temperaments. Thankfully I didn't let Ronald get to them and they are now exploring their future run by themselves. Thank you all for your help.